Autofocus prediction

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ohara

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I'm fairly new to sport photography, but I was shooting some runners in a marathon recently. I know the basics but I have never done it before. I took about 400 shots and I would say probably 40 of them were in sharp focus. I know the success rate in photography can be low for sports but 10% is pretty bad.

I was using a Canon 70-200mm IS f/2.8L lens on a 7D. For the most part I was on aperture priority at 2.8, and auto ISO. The camera was shooting about ISO 125 with 1/250 shutter speed.

I had the auto focus set up for spot, using the centre point, and shooting mode was high speed continuous.

Now the problem I have had is that in a lot of my shots, the AF is slightly off. Shooting at f/2.8 and mostly at 200mm I know the depth of field is rather shallow. In a lot of the photos it looks like the camera has focussed slightly behind the subject, so in a lot of the photos the person behind the one I was trying to shoot is sharp. There are very few where my intended subject is in sharp focus. I'm guessing that the camera was locking focus, and then in the split second between focussing and shooting the subject had moved slightly closer and thus out of sharp focus.

My question is, am I using the camera wrong or is this a limitation of servo AF? I have seen the autofocus on the 1D X and it is incredible, and obviously at 1/5 of the price I don't expect the 7D to be anywhere near as good but with the exception of the 1D Mark IV the 7D was probably the best sports camera of its time.

Oh and I should add my technique was just to put the centre point over the subject and hold the shutter button down. I was hoping that the excellent AF and the 8fps shooting speed of the 7D would make up for my lack of experience but I was wrong.
 
Sounds to me like tis is down to your shallow depth of field.

From what I've heard the 7d focus system can take a bit of getting used to, so maybe just the wrong setting.
 
I understand, I haven't used the 7D much before. The 5D Mark III has an incredible AF system (I believe it's from the 1D X) but unfortunately was unavailable on the morning. I elected for the 7D because of it's AF and the fact it can shoot 18mp at 8fps.

I was wondering whether it had some mode or setting where it could predict closing movement and compensate with the AF or not. Next time I'll try using a faster shutter speed too, if that helps.
 
I ahvent got a 7d or used one but read enough to know theres nothing wrong with the AF in this condition..certainly not a af limitation thing..

First thing your doing wrong is the shutter speed and iso... 250 shutter is far too slow for moving subjects even coming towards you.. the iso is rediculously low.. you could easy go iso 400 or even 800 and upped the shutter to more acceptable speeds.. I am guessing your main problem is too slow shutter.

dont use spot metering unless you know your going to be pointing at the same mid colour all the time.
SCRUB THE ABOVE I THOUGHT YOU SAID SPOT METER ... Your right wiht single spor focus IMHO.

was you in aiservo.. you could be focusing then the runner running out of focus if not.
 
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I thought the shutter might have been a bit low. I wasn't using spot metering, I was using evaluative. When I was talking about spot, that's the AF point that I was using. There's a bunch of different modes, like all points, groups of points, points, and spot. Spot is basically the very middle part of a point (like using spot metering vs center weighted average, it takes a sample from a much smaller space).

Yes I was in AI servo, I tested by holding the shutter half way down and moving around, and it refocused fine.

Like I said when the runner I was wanting to photograph was approaching I just put the centre point over him and held the button down and did my best to track him as it was shooting. I think I did about a 50 shot burst at one point and he's in dead centre in the majority of them but only about 5 have him in sharp focus, and in some of them the focus is COMPLETELY out even though there was nothing between him and the lens. I didn't touch the MF ring.

Edit: I see you are a sport photographer, I don't mean to insult you by having to explain AF modes!
 
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Here's a test shot I did of the timing car just to make sure I had the AF/etc set up properly. It's nice and sharp and in focus, and it moving at approximately the same speed as the race leaders (obviously).

(excuse me hosting it on facebook :))

615850_10152243650235514_917958376_o.jpg
 
Use single point AF point, The centre one should suffice.Turn the AiServo Sensitivity down a little and when shooting, dont release the shutter straight away, Allow the AF to aquire for about 1/2 sec to a sec before releasing the shutter. I can't remember the CF numbers but its online or in your manual.

The AF on the 7D is more than capable to track runners. Just make sure you allow the AF to achieve focus before releasing the Shutter.

ISO 400 is very useable with the 7D so this should allow you to use a fast shutter speed.

If you are still getting a low keeper rate, up the Aperture half or third of a stop. But as I'm sure you know, this will reduce the shutter speed by the same third or half a stop.
 
to be fair the car is moving towards you but smoothly.. ie not slight up/down movemant that a runner has :)
 
Can you confirm you were in the AI Servo focus mode?

Reading your post I suspect not, you haven't mentioned it...
 
Where were you focusing on the runners?
As Tony says they are bobbing up & down slightly also their hands & arms are normally pumping in front of their bodies as they are running which can sometimes throw the af momentarily. I find a good place to af on runners when using the centre point is the number on the front of their running vest's which is high contrast. If using other af points always look for a high contrast areas.

I had a 7d some time ago & found I had to PP slightly differently as straight out of camera the files did seem a little softer when compared to my 1D series bodies but once pp'd with a tad more sharpening (or set in camera) they were fine. :)

Stew.
 
I reckon that it's down to using spot focus, which is primarily designed for macro. Use point + assist points, which is far more accurate for tracking.
 
RichardtheSane said:
Can you confirm you were in the AI Servo focus mode?

Reading your post I suspect not, you haven't mentioned it...
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Yup he has Richard - twice! :p :D
 
DemiLion said:
I reckon that it's down to using spot focus, which is primarily designed for macro. Use point + assist points, which is far more accurate for tracking.
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I really don't know wether to laugh or cry .......


10 yrs using spot focus (me and every other sports photogrepher i know) and now I am told its for macro users ?
 
KIPAX said:
I really don't know wether to laugh or cry .......


10 yrs using spot focus (me and every other sports photogrepher i know) and now I am told its for macro users ?
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No mate, you use "centre point" the 7D has a totally different AF mode called "spot focus"

You basicially select any focus point and then use "spot point" to select an even smaller area within that focus point, its deffo not to be used for moving subjects and is only really useful if you want to pin your focus down to a milimetre os something silly like that, use it to focus on Gnats nadgers or the stamen of a flower but deffo not for sport as it over rides the AI Servo to some degree

The OP just needs to use single/centre point and AI Servo and forget about spot point

Nikon user to the rescue of Canon guys again
 
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KIPAX said:
I really don't know wether to laugh or cry .......

10 yrs using spot focus (me and every other sports photogrepher i know) and now I am told its for macro users ?
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Your camera doesn't have spot focus Tony. It has single point.

You can laugh now.
 
The 1DX does have spot focus...Pg 69 & 72 refers Referred to as Single Point Spot.

It is recomended that it be used for Macro work... I tried it last week shooting Rugby, My keeper rate went down from the previous week when I used Single point... I went against the advice and failed...
 
Tugster said:
The 1DX does have spot focus...Pg 69 & 72 refers Referred to as Single Point Spot.

It is recomended that it be used for Macro work... I tried it last week shooting Rugby, My keeper rate went down from the previous week when I used Single point... I went against the advice and failed...
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Cheers Simon. I hadn't realised that it had been included in the 1Dx. The problem with it is that it is too small an area to get decent contrast! It isnt bad for close up static work, but risky for anything else.
 
SORRY....WRONG AGAIN :)

Note to self... don't post when drinking :)
 
Thanks for the replies. So I see I made a number of mistakes! It was my first time and I did not have much time to get set up due to having to rush around in the morning.

I'll hopefully be shooting another one in January but this time with the mark II version of the 70-200mm f/2.8 IS lens, which is quite a lot better. I will also remember for next time:

bump ISO up to 400-800
shutter speed much faster
higher f-stop for more DoF
use single point or single point+assist instead of spot AF

Thanks again all.

Ps. KIPAX, do you own a 1D X?
 
ohara said:
Ooh very nice. I would love to get my hands on either!
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I dont own them.. my business does... if i wasnt using them to make money i would still be on a 10d with a sigma 70-200 :) tools of the trade is what they are..
 
Also be sure to be choosy about your point of focus. Not enough contrast (say, on a runner's white shirt) will make focusing tricky for the camera. Also if its daytime perhaps push up to F4 on a big tele - the extra DoF is worth it if your subjects' movement is dynamic (ie. all over the place). Simply pointing the camera at someone is not enough for best focus.

Not exactly related here but I would also recommend separating focus from shutter (back button focusing), and learn to control each individually. The point is then that you should be finding focus before you take the shot.
 
Oh and if you have reliable AF points either side of centre, don't be afraid to use them if it helps composition. If I roll around to portrait on, say, a footballer I will also move the AF point up to the face so that I track the head and get the expression sharp rather than the feet.

That may not be a popular method but I find it works for me.
 
dafphotographer said:
Also be sure to be choosy about your point of focus. Not enough contrast (say, on a runner's white shirt) will make focusing tricky for the camera. Also if its daytime perhaps push up to F4 on a big tele - the extra DoF is worth it if your subjects' movement is dynamic (ie. all over the place). Simply pointing the camera at someone is not enough for best focus.

Not exactly related here but I would also recommend separating focus from shutter (back button focusing), and learn to control each individually. The point is then that you should be finding focus before you take the shot.
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Weve covered these in some depth before though it doesnt harm to remind newbies of the benefits
 
dafphotographer said:
Oh and if you have reliable AF points either side of centre, don't be afraid to use them if it helps composition. If I roll around to portrait on, say, a footballer I will also move the AF point up to the face so that I track the head and get the expression sharp rather than the feet.

That may not be a popular method but I find it works for me.
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As above reply, some cameras can automate this for you
 
Apologies, i'm a noob around here myself.

And to be clear, I'm referring to moving your focus point rather than simply relying on surrounding AF points assisting the selected AF point. They are different in their execution in that you're actively choosing to focus on a different part of the subject, rather than the camera utilising similar AF points to achieve focus where otherwise it was difficult.

With focusing I find we should take the power back sometimes! We have powerful cameras but ultimately it requires practised skill and good operation.
 
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dafphotographer said:
Apologies, i'm a noob around here myself.
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Sorry mate, wasn't looking for one or wanting one, misunderstanding. :thumbs:

Didn't mean newbies to the forum but to shooting sport in general.

You'll quickly get used to me David, im a Bovril sort as is KIPAX, tell it straight or don't tell it.

Welcome anyway and keep posting, would love access to come of the events you cover but a lot more goes on down the smoke than up my neck of the woods
 
dafphotographer said:
And to be clear, I'm referring to moving your focus point rather than simply relying on surrounding AF points assisting the selected AF point. They are different in their execution in that you're actively choosing to focus on a different part of the subject, rather than the camera utilising similar AF points to achieve focus where otherwise it was difficult.

With focusing I find we should take the power back sometimes! We have powerful cameras but ultimately it requires practised skill and good operation.
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Was meaning that myself, doesn't the MKIV and IDX have a menu set up where upon switching the camera from horizontal to portrait it also moves the focus point to a pre determinted one so you dont have to manually move the focus point, ie 2 points further up in portrait mode so the AF point auto switches when in portrait mode and back again automatically when you switch back to landscape mode, i know when i had the MKIV it could be set up to auto switch.

Im a Nikon shooter now and did have a firmware hack to do the same thing with the D3S but ive lost that after Nikon reset my camera when in for some work and cant find the hack anywhere now.
 
dafphotographer said:
With focusing I find we should take the power back sometimes! We have powerful cameras but ultimately it requires practised skill and good operation.
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Anticipation and knowledge of the sport youre shooting plays a big part, you guys who cover lots of different sport must have brains like sponges to soak everything up, me, well as soon as i lean over to one side the brain empties on the ground.
 
Can't add too much in terms of specifics for getting good shots of runners but as a fellow 7D owner I can't say don't be afraid of upping the ISO.

There are a lot of horror stories about the 7D and "noise" and yes, there are cameras that handle higher ISOs better but provided the image is exposed properly, with a little PP noise reduction you'll still end up with usable images.

I took several shots at a rugby match on Saturday using ISO6400 and ISO12800, never going to win any prizes but they're better than nothing ;)
 
Russ77 said:
...but provided the image is exposed properly, with a little PP noise reduction you'll still end up with usable images.
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I can't second this enough. Get the right exposure, don't rely on PP! I think a lot of people don't realise how an image is compromised by getting the exposure wrong, especially at night with all those shadows.

Most cameras these days have incredible ISO depth, so use it. You're not gaining anything by underexposing and trying to pull it back in post.
 
dafphotographer said:
I can't second this enough. Get the right exposure, don't rely on PP! I think a lot of people don't realise how an image is compromised by getting the exposure wrong, especially at night with all those shadows.

Most cameras these days have incredible ISO depth, so use it. You're not gaining anything by underexposing and trying to pull it back in post.
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That holds for 99% of cameras and shooting scenarios but there are the occasional times when there will be an exception to the rule, my old 1DMKII maxed out at ISO 1600, even with expansion on you only get 3200 and at the ground i was shooting at i was only getting 1/125th sec which was no good at all.

ISO expansion in itself is basically the camera underexposing and pulling it back, i was then underexposing up to 2 full stops to get anything useable with the shutter speed and at the same time forcing myself to only shoot to fill the frame as any cropping would have been making the noise even worse.

Final output images looked like apple crumble but in print at 72dpi they were very useable, i got paid, the paper got some useable images, winner all round.
 
Gary Coyle said:
Was meaning that myself, doesn't the MKIV and IDX have a menu set up where upon switching the camera from horizontal to portrait it also moves the focus point to a pre determinted one so you dont have to manually move the focus point, ie 2 points further up in portrait mode so the AF point auto switches when in portrait mode and back again automatically when you switch back to landscape mode, i know when i had the MKIV it could be set up to auto switch.

Im a Nikon shooter now and did have a firmware hack to do the same thing with the D3S but ive lost that after Nikon reset my camera when in for some work and cant find the hack anywhere now.
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Yes the 1 dx and 5d3 both have this feature..
 
To the OP = no need to worry about the focussing capabilities of the 7D.

There are plenty of people shooting BIF (birds in flight) with the 7D and getting fantastic results.

Also whilst the 70-200/2.8 II is great, so is the version I that you have.

It's just down to technique and you picked up on. Remember you can post your next ones in the photo sharing section next time.
 
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